Motor-transmission system



Feb. 28, 1961 E. c. BAILEY ErAL 2,972,900

MOTOR-TRANSMISSION SYSTEM '7 Sheets-Sheet 1 Original Filed Jan. 18, 1945 Feb. 28, 1961 5. c. BAILEY E'rAL MOTOR-'TRANSMISSION SYSTEM Original Filed Jan. 18, 1945 7 Sheets-Sheet 2 Elim Feb. 28, 1961 E.c.BA1LEY Erm.

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MOTOR-TRANSMISSION SYSTEM original Filed Jan. 18, 1945 7 SheetsSheet 5 G R S i ,n MEM M MM@ m VBN T W A 05 M TY E mm Q EW YI B EE m @xl m. w

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muuu L UUUUU mm Q, ES ES .SQ mmE kmb United States MOTOR-TRANSMISSION SYSTEM Emmett C. Bailey, Riverside, Calif., and Wesley Spangenberg, Takoma Park, Mtl., assignors to the United States of America as represented by the Secretary of the Navy 2 Claims. (Cl. 7'4-354) (Granted under Title 35, U.S. Code (1952), sec. 266) This invention relates to power drive mechanisms, and is a division of my copending application Serial No. 573,398, led January 18, 1945, now Patent No. 2,959,066, for Motor-Transmission System. The invention has as its primary object the provision of simple, compact and eilicient means for producing a variety of motions, by means of which two distinct objects, as for example the control surfaces of an airplane, may be moved either independently of one another or in an interrelated manner.

Another important object of the invention is to provide such a mechanism adapted to furnish power actuation of the control surfaces of an airplane of Vthe type disclosed in the copending application of William Hunter Ayres Boyd, Serial No. 524,431, iiled February 29, 1944, now Patent No. 2,807,261, wherein two movable control surfaces are provided for controlling the ight path of the aircraft and its lateral stability, the control surfaces consisting of two elevons, one located in each wing. More specifically the present invention provides means whereby (l) both elevons may be moved upward simultaneously, or (2) both may be moved downward simultaneously, or (3) either elevon may be moved upwardly While the other is moved downwardly, or (4) either elevon may be held stationary while the other is moved either upwardly or downwardly. Still another object is to provide such a power drive system capable of transmitting any of the aforesaid movements or combinations of movements but which is powered by a single unidirectional motor.

Still another object is to provide a power drive sys' tem which includes a novel gearing and reversing system,

in which the gear reactions are so balanced one against' the other as to permit a small operating force to effect the clutching and declutching of gears which are. capable of transmitting a relatively large torque. v

The present invention also includes among its more specific` objects the provision of a novel gearing system including a shiftable gear carrier adapted to be moved to either side of a neutral position` to establish a geared driving connection in either direction and which incorporates a novel synchronizing arrangement eliminatingV clashing ofthe gears.

arent a 2,972,900 Patented Feb. 28, 1961 ing one of the solenoids together with portions of the linkage and gearing;

Figs. 8, 9, and l0 are detailed sectional views taken substantially on the lines 88, 9-9, and 10-10, respectively, of Fig. 6, and looking in the directions of thearrows; t

Fig. l1 is a sectional detail taken substantially on the line 11-11 of Pig. 1, and looking in the direction of the arrows;

Fig. 12 is a partially exploded perspective view of one of the gear carriers, together with the gearingv carried thereby; Y v

Fig. 13 is a diagrammatic view of the gearing carried by and directly cooperating with one of the gear carriers, illustrating the torque reactions of the gears and the resultant effect upon shifting of the gear carrier;

Fig. 14 is a top plan view of the linkage, corresponding to a horizontal section taken substantially on theI line 14-14 of Fig. 1, and looking in the direction of the arrows;

Fig. 15 is a perspective view of the supporting frame or chassis, partially broken away;

Fig. 16 is a diagrammatic view of the entire power transmission system and interconnected elevons, showing the parts in the positions they assume when both elevons are simultaneously elevated;

Fig. 17 is a similardiagrammatic view showing the parts in the positions they assume when one of the elevons is raised and the other held stationary;

Fig. 18 is a diagrammatic plan view of a glider provided with power driving means constructed in accordance' with the present invention for operating the con- Another object is to provide a novel system of linkage for the derivation of theseveral relative motions listedl above.

Fig. 1f is a front elevational view of a device incorporating the principles' of the present invention, with a part of the casing removed; t

Fig. 2 is a top'plan view of the same, also with cover removed; y

Figs. 3,4, 5, and 6 are sectional views taken substantially on the lines 3 3, 4-4, 5.-5, ando-6,y re-V spectively, of Fig.` 2, and looking in the directions of the arrows; t

Fig.V 7 is a fragmentary inverted plan .view taken as indicated'by vthe line and arrows 7-7 ofFigI, Vshowtrol surfaces thereof; y v

Fig. 19 is a diagrammatic plan view of a modified linkage arrangement; and

Fig. 20' is a diagrammatic .view Kof the gearing illustrating the mathematical considerations involved in determining the position of the carrier-mounted gear.

The principal components of the preferred form of the invention illustrated in Figs. 1 to 18 inclusive of the drawings comprise (l) a motor M, constituting the sole sourceof power and which constantly rotates in one direction while the system is in operation, (2) gearing, best shownin Fig. land generally designated G, which serves the several functions of torque and speed conversion, division of the' drive into two trains, and the provision of individual reversing means f o'r each such train, (3) electromagnetic gear shifting means S, S', (4) a novel linkage system, generally designated L, constituting motion translating means, and which insures a desired coordinated interrelation of the motions imparted to (5) the two power arms A, A', by which the elevons E, E', aircraft are moved to direct its llightand control its lateral stability.

The general mounting of the unit in the aircraft, and the manner in which the power arms are connected to the elevons to actuate the latter, are best shown in Figs. 16,17, and 18. n v, v

All of the components are carried by a box-like sheet metal frame or chassis 1 (Fig. 15), having a front wall 2, side walls 3, 4", and a pair of spaced bottom or floor plates 5, 9. lMounting brackets 6, 7 `are provided at either end of the chassisfor mounting rthe same upon a transverse bulkhead asr 8 of the aircraft. The aircraftfor which the preferred unit disclosed herein is particularly designed is illustrated in Fig. 18 as of the type, disclosed inv the Boyd application above referred to, wherein the shipV is caused totcliinb by depressing both elevons, E, E', to' dive by'asling yboth elevons, to turn by raising one elevton while depressing or holdingthe n other stationary, and in which lateral trimming is effectedl constituting the control surfaces of thel aeration by raising one elevon and lowering the other. The motor and the screw drives which constitute the last elements of the gear trains are contained within the enclosure. of the walls 2, 3, 4, and S, while the linkageY is arranged between the floor plates S and( 9, and the remainder of the gearing and the gear shifting solenoids are mounted on the front wall 2.

The motor M is mounted by means of screws 12 approximately centrally of the front wall 2 as shown particularly in Figs. l and 2 and carries on the outer end of its shaft the drive pinion 13. A centering boss 14 on the front end of the motor casing is fitted in an aperture in the front wall 2 to locate the motor. Pinion 13 meshes with idler gear 15, which rotates on a bearing post fixed in the wall 2. Gear 15 drives similar gear 16 also iournaled on a post fixed to the wall 2 and arranged on the opposite side of gear 13. Gears 15 and 16 constitute the rst gears of two reduction trains, each of gears 1S, 16 having a smaller gear 15a and 16a, respectively, formed integral therewith and constantly meshing with a reversing pinion 17, 18, the reversing pinions being mounted on shorter bearing posts located directly beneath the bearing posts of gears 1S, 16 as shown in Fig. l.

Cooperating with each pair of gears 15A-+17 and 16a-1S is a gear carrier 19, 20. Since these are alike (but symmetrically reversed) description of one (19) will suice. Front and back plates 19a, 19b of the carrier 19 are fixed in spaced alignment` by a plurality of rivets as 19C, each of which is surrounded by a bearing and spacer sleeve 19d serving as a support for one of the gears 21,22, 23, 24, and the roller 19e. Roller 19e in cooperation with detent arm 25. serves'asyieldable centering means for the carrier, normally maintaining it in a centered position in which the pinions 21, 23 carried by hte extremities of its forked arms are free of the Agears 15a, 17. Detent arm 2S is pivoted` at 26 `on the front plate 2 and biased downwardly by the spring 27 extending between the arm 25 andcarrier plate 19. Gears 21 and 23 ,mesh with the gears 22 and 24, respec-` tively, and the latter are in continuous mesh with the large gear 28 which is keyed, to shaft 29 as by appropriate squared portions,vthe gear and the carrier assembly being held onV the end of the shaft by a pinned collar 30. It will be seen that gear 28 and shaft 29`may be driven in one direction by rocking the carrier from the centered position in which it is shown in Fig. 61to bring gear 21A into mesh with gear 15a and in the opposite direction by rocking the carrier to bring gear 2 3,into"mesh with gear 17. r l i A ball bearing holder 31 carried by the front wall 2 (Fig. 4) supports the forward ball-bearing for shaft 29, the rear end of which shaft is supported .by a ball-bearing in a pedestal 33mounted on the lower door plate 5] The solenoid shifter assemblies S, S' referred to above function to rock the carriers 19, 20, respectively. Each such assembly includes a pair of solenoid/coils as 35, 36 (Fig. 6). When both of these are deenergized the carrier remains in the centered position in which the drive'is interrupted, while the selective energizatiorr of the coils permits rocking the carrier in either direction vfor oppo-v site drives as noted above. The construction of the coil assemblies is ,clearly shown in Figs.' 6, 7I and 48. Each coiljis wound on a cylindrical form of, insulating 58 held in and projecting inwardly from the bores in the lower end cap 42 through which the armatures project. Suitable non-magnetic washers indicated at 50 serve to absorb the impact of the armature sections against the stationary cores and also to reduce the etects of residual magnetism. The projecting ends of the armatures are slotted at S1, S2 and have loosely pinned in the slots the links S3, 54 which are connected by a rocking lever 55 pivoted on a post 56, centrally mounted on cap 42. An extension link 53a of link 53 connects the solenoid armature linkage to the gear carrier 19.

Carrier 20 together with its gearing and shifting means constitutes similar means for driving and for controlling the direction of rotation of a shaft 62 arranged in similar position to the shaft 29 but near the opposite end of the assembly, the position of all of the parts being substantially symmetrical with respect to a vertical longitudinal center plane, as will be apparent. Thus it will be seen that rotation of motor gear 13 may be transmitted to either or both of shafts 29 and 62 so that the latter may rotate together in the same or opposite directions or may rotate singly in either direction depending upon the energization of the solenoids.

Fig. 13 shows the relative positions of the gears in the carrier and also the driving gear 15a and the reversing gear 17, gear 21 being engaged with gear 15a to impart clockwise rotation to gear 28 and shaft 29. The driving force on gear 21 supplied by the gear 15a and represented by the arrow F2 acts on the gear carrier at an eiective radius indicated by the arrow r2, in a direction to tend to disengage the gears. This disengaging torque is equal to the product F2111 and tends to rotate the gear carrier in a clockwise direction. Hence to keep the gears engaged a torque of this magnitude must be applied to the gear carrier in a counterclockwise direction. By the incorporation of the gear 22 in the gear carrier between the gears 21 and 28 this counterbalancing torque on the gear carrier is introduced, since'the reactive force of the gear 22 rotating in a counter-clockwise direction is a force, represented by arrow F1, acting on the carrier in the counter-clockwise direction. Neglecting the frictional force necessary to drive the gears 21 and 22, the tooth load between gears 22 and 28 is the same as that between gears 21 and 15a, i.e., F1 will he equal to F2.

The reactive force F1 will be directed through'the pitch point along the line of contact between gears 22 and 28 and hence at a radius R1 from the pivot point of the gear carrier. The radius R1 is therefore tixed once the size of gear 28 is xed. F2 is directed in like manner through the pitch point along the line of contact between the gears 21 and 15a, but by selecting the pitch point along the pitch line of gear 15a the direction of the force F2, and hence the length of its effective radius of application R2, Vmay be varied. By ythe proper selec-- tion of the pitch point, the torque FzRZ may be made to bear such relationship to the reactive torque F1R1 as may be desired. If the radius R2 is made less than radius R1, the dsengaging torque FZRZ will be less: than the engaging torque F1R1 and a force would berequired to pull the gears from engagement. The frictional losses l in the gearsV 21 and 22 tend to make F2 slightly greater material`37,k38, and sheathed by a metal cylinder.V 39,401

The end caps 41, 42 are held together byrscrews 43 which' extend through cap 42 and are threaded into cap 41. .l The solenoid :cores are kof iron andcomprise. adjustablesta? tionary portions 44,` i5-threaded through capY 41 and locked in place by nuts .46, 47, and `slidable'armature portions 48, 49. The armatures are smaller thang'the bores in rwhich they travel andiare,.cent`ered,to preventV rubbing contact over the' entire surface area, -bynon-rnagnetic central guide rods 48a,'49a extending from theV upper ends ofthe armatures rintovcentral boresi44q, .4521, in thestationary cores," and by non-magnetic guide rings than F1, so .that once these losses are 'determined proper allowancemay be made.4 In my preferred embodiment the'desgn is such as to make R2 very slightly greater than R1 and resultantly the. disengaging' torque F2121' very slightly greater than the active torque F1R1. This assures prompt and automatic declutching when the solenoid is tie-energized. The solenoid, on the other hand, needs to supply only a comparativelyy small force to keep the gears in engagement, namely, the difference between- H the disengaging and engaging torques.

Upon reference to Fig. 13 it will beseen that if'the position of the drivable gear 21 where changed (withinl limits) by rolling it around the periphery of the driving S gear 15al in a .counter clockwise direction to a new position farther to the left as viewed in the figure, the` direction of F2 would change in a manner to decrease R2; and conversely, if the drivable gear were placed to engage the driving gear at a point displaced in the opposite direction the length of R2 would be increased.

In the particular arrangement of gearing in this device, R2 was chosen of a length such that if F3 denotes the sum of the frictional drags of the drivable and idler gears 21, 22, the two counterbalancing moments would have the mathematical relationship:

(F2-|-F3)(R2) F1R1 by an amount less than the resisting moment supplied by the solenoid.

After the proper value of R2 is determined by the design considerations, the position'ofthe drivable gear with respect to the pivot-poifof'the carrier Vand the driving gear may be determined by the following mathematical considerations:

Referring to Fig. 2O

B=radial distance of drivable gear'from pivot pointof carrier. OB determines the location of the drivable gear with respect to the pivot point` without regard to the position of the carrier with respect to the driving Vgear'.

OC--radial distance of the driving gearfrom the pivotpoint of the carrier. OC lixes the location of the driving gear with respect to the pivot point of the carrier without regard to the position of the carrier with respect to the drivable gear. The pitch point of the driving gearand drivable gear can be changed only by a change in OB or OC. For the purpose of this derivation OC will be assumed to be lixed by the geometrical considerations of the gears chosen and OB will be the variable to change the relationship of the driving gear and drivable gear.

` CV=pitch radius of driving gear. CV can b e varied onlyl by changing the size of the driving gear.

VBH=pitch radius of drivable gear. VB can be varied only by changing the size of the drivable gear.

Hence CB=CV+VB=the surn of` the pitch. radii of the driving and drivable gears.

Angle WCV=a=pressure angle ofl the gears chosen and is therefore xed once the particular type of' gear' tooth to be used is chosen.

CW is perpendicular to F2 Aand is by definition equal to the radius of the base circle of the driving gear.

Angle OCB is the angle between the line connecting the pivot point of the carrier with the center `of the driving gear and the line connecting the center ofthe driving gear with the drivable gear when the d rivable geark is in meshing engagement with the driving gear. y

R2=radius at which the line of action F2 acts upon the gear carrier. R2 is therefore perpendicular to F2.

By the law of cosines it will be seen that v (i) OB2=0C2+CB22(0C)(CB) eos OCB in which OC and CB are xed once the driving gear` is located, by pure geometrical considerations and once the diameters ofthe driving and drivable gears are chosen.

Angle OCW/:CGH because R2 is parallel with CW cos OCB-cos (OCW-f-WCV)A d Cos"OCB=cos OCW cos WCV--sin OCW sin WCV.

To determine cos OCW construct CH parallel with F2 and extend R2 at'J, which makes YH]=CW. Then aeraeoo which can be reduced to the form I0BZ='K1fK2R2 from which it'can be seen that R2 Vvaries withOB in s'uch a manner that if OB is increased, R2 `will decrease to zero and thenmreach a maximum negative value.

It will likewise be seen t'hatif OB is decreased, R2 will be increased until it reaches a positive maximum.

With the gearing arrangements shown, it will also be noted that as the gear 21 is brought into engagement with the gear 15a by counterclockwise rotation of the gear carrier, clockwise rotation is imparted to gear21 as gear 22 rolls about the periphery of gear 28, which under this condition is at rest. The engaging teeth of gear 21 will therefore be moving in the same direction as the engaging teeth of the driving gear 15a. The velocity of movement of the carrier is preferably such that during movement'of the gears into engagement, the angular velocity of gear 21 equals the angular velocity of gear 15a. The gears are thus synchronized and the teeth are fully engaged before they are required to transmit power.

Although 141/2 degree involute gear teeth are shown, specially designed pointed teeth could be used if dei sired.k At speeds of the drive and reverse gears` 15a, 17 up to approximately 3000 r.p.m., special gear teeth have not been found necessary.

While the above description has been confined to the engagement of gear 21 with gear 15a resulting in the driving of the gear 28` in a clockwise direction, gear 23 is obviously engageable in similar manner with gear' 17 to impart counter-clockwise rotation to gear 28; Since the arrangement of the gears is symmetrical about the horizontal axis of the gear carrier, similar force re actions areirnparted to the gear carrier in an identical manner but directed oppositely. 2

Shafts 29 and 62 are formed intermediate their endsy as screws and eachcarries threaded thereon a traveler nut, as 63, 64, longitudinally moveable by rotation of its screw. Referring to Figures 4 and 5 showing in de-y tail the parts appurtenant the nut 63 and bearing' in mind that similar parts are provided in connection with nut 64, it will be noted that a U-shackle 67 having top and bottom plate' portions is pivoted to thetraveler. Trunnion studs 68 project froml thev shacklel in which they are threadedly secured, into holes in the traveler nut, while similar studs pivotally connect the shackle at its other end to a crank composed of spaced upper and lower arms 70, V71 united to a hub pinned to a shaft 73V extendingr thereinto. Nut 63, when actuatedy by rotation of the screw shaft 29, rotates the vertical shaft 73. A duplicate mechanism transmits rotationv fromv screw shaft 62 to shaft 74 through an arm 72. y

The details of the linkage, L, through which the ro tation of shafts 73 and 74 is transmitted ,to the paralf lelogram systems comprising arms 75, 77, 84, 85,; and

76, 77a, 81,` 82 of the remote control unit, are shown in Figs. 14, 16 and 17. Fast upon shaft 73. is an obtuse-angled double-armed bellcrank type lever 77. The

longer arm of bellcrank 77 is -pivotedto abellcrank 75 formed of elevon operating Larm ,A and thefintegralI 7 forwardly projecting work arm 75, at the iunction the arms.

'Illel shorter arm of bellcrank 77 is pivotally connected by link 80 to the short arm of a bellcrank type lever 77a which is similar to bellcrank 77 but inverted in position and loose upon shaft 74. The longer arm of bellcrank 77auextends outwardly and is pivotally attached to the bellcrank comprising elevon operating arm A' and work armV 76, mounted with its arrn A' projecting outwardly similarly to bellcrank A -75 but o n the opposite side of the unit. Arm 76 is connected by a link 81 to crank 82 which is pinned to shaft 74. A similar link 84 pivotally connects the arm 75 `with an arm 85 which is free on shaft r73. Crank 82 and arm 8S are joined at their outer ends by a link 86. rlhe bellcranks A-75, A76 are thus supported by individual parallelograrn systems, thesel two systems being interconnected by the diagonal and transverse links 80, 86. The extremities of A, A' are linked to the elevons bydrag links D, D' and lever arms a, a.

From the foregoing and by reference to Fig. 16 .it will be seen that rotation of shaft 73 in the counterclockwise direction, for example, while shaft 74 remainsl stationary, will simultaneously collapse both parallelogram systems in opposite directions in translating the elevon operating arm A rearwardly, moving the link 80 to the left, as viewed in Fig. 16, moving the longer arm of bellcrank 77a rearwardly, and translate the elevon operating arm A aft. Both elevons are accordingly raised, tending toicause the ship to dive withoutl turn-` ing laterally. Similarly, clockwise rotation of 73 will result in forward translation of arms A andv A' to induce climbing of the ship. Clockwise movement of shaft 74,

while shaft 73 remains stationary and the unit is as shownV in Fig. 16, will on the other hand simultaneously expand both parallelogram systems in the same direction to move the outer end of arm A aft through arms 82 and 81, at the same time moving outer end of arm A forward through the movement of members'86 and 84. Rotation of shaft 74 in a counter-clockwise direction will move the outer end of arm A' forward and the outer end of arm A aft. The parallelism of the equal arms 77a and 81, and 77 and 84 insures substantially equal travel of the outer ends of the elevon operating arms for equal angular displacement of shafts 73 and 74. Simultaneous rotation of the latter shafts produces forward or rearward movement of the outer end of one or the other of arms A, A at an increased rate while the opposite operating arm remainsy substantially sta-y tionary. Y

' As shown in Fig. 17, simultaneous y'rotation of both of the shafts 73, 74, in a counterclockwisedirection, as

he direction of the latter motion depending upon the directions in which the shafts are rotated.

It will be Vseen from the foregoing that-the elevons.

89Yand-90 having pivoted,k arms disposed in the path ofk movement of the arms 70, 72, to interrupt energization of the solenoids when a safe extremity of movement of the work arms has( been reached. A metal cover 92 is.

also provided lto electrically shield the apparatus and protect it from the weather.

In the modified linkage arrangement shown in Fig. 19,

substantiallyV similar action is secured with a somewhat simpler assembly. SimilarY bellcranks comprising elevon operating arms A, A and work arms 175, 176 are emv ployed to actuate driven elements such as the elevons of an aircraft of the type referred to above. The two bellcranks are movable-bodily in a manner essentially translatory by means of a driving bellcrank 177 analogous to the be1lcrank177 `of the embodiment first described, operable by a driving shaft as 173 and connected at its outer end to the bellcrank A, 175 while its inner, shorter arm is attached to amotion reversing'link 180 which actuates the bellcrank A'-176 through an intermediate bellcrank 17711. The parts thus far described will be seen to be fullyV equivalent to those of the first embodiment for effecting opposite synchronous pivoting of levers 177 and 17711. In lieu of the three links 81, 86, 84, however, a single rigid link 200 is articulated to the ends of ,the work arms 175, 176 and so maintains the bellcranks A, 175 and'A 176, in essentially parallel relation. When'the 'last mentioned bellcranks are to be pivted in the same direction about'their supporting pivots,4 power is applied tothe ends of arms 175, 176 through the agency of' a driving arrn 182 secured to and drivable by the shaft 174 (which corresponds to the shaft 74 of the rst embodiment) and link183 connected to. pivot 18S of arm 175, while link 200 transmits the motion to driving gears, a driven gear spaced from said driving viewed fromv above, raises the port elevon whileallowing l the starboard elevon to remain substantially stationary the resultant positions of the combined actuation of the twolinkages between the parallelogram systems. The operating arm vA is thereby moved aft more rapidly and farther than when actuated by rotation of onlyone of the Shafts .73, 74, Since it is moved both by the bellcrank 77 and by the crank' 82, which actuates it through the agency of the links 8.634'to increase its rearward travel. v

On the other hand the counterclo'ckwise rotation of crank 82 tends to movethe outer endof armA forward Awhiley itis at the same time urged aft by the motion imparted thereto through link 80. Thels'tarboard parallelogram system assembly accordingly collapses, inclining outwardly and rearwardly as shown in Fig. 17, in such manner that the outerfend of its elevon operating arm remains substantially stationary. When both of the shafts 73, 74 are revolved clockwise, the port elevon is depressed while the starboard elevon remains stationary, as will be apparent, while rotation of the shafts in op gears, a carrier vmounted for pivotal movementabout the axis/of the' driven gear, two sets of gears mounted on said carrier, each set of gears being intermeshed and having one gear which is in constant mesh with the driven gear, each set of gears having another gear, one of which is engageable with one of the driving gears upon pivotal movement ofthe carrier, the other of which is engageable with the other of the driving gears upon pivotal movement of the carrier. in an opposite direction, whereby either a clockwise or counterclockwise torque may be transmitted to the driven gear, the driving, driven and s carrier-mounted gears being so` positioned that in either posite-directionslresults in holding the port elevon `sta-V t'ionaryrwhile vraising or lowering the starboard elevon,

driving position of the carrier theline' of action between the operative driving gear and the carrier mounted gear meshed therewith is substantially tangent to the driven gear, whereby the moment of the force, exerted by either driving gear on its respective meshing carrier-mounted gear and directed along the line of action between these two gears, about the axis of rotation of the carrier is substantially balanced by the moment of the reactive force, exerted bythe driven gear upon the corresponding one of the constantly meshing carrier-mounted gears and directed along theline of laction between these two gears, whereby any tendency of the carrier to pivot about its axis, caused .by such moments, is substantially reduced.

2. Transmission means comprising driving and driven gears spaced from one another, a carrier mounted for pivotal movement about the axis of the driven gear, a pair of meshed gears mounted on said carrier the iirst of which is in constant mesh with the driven gear, the second being engageable with the driving gear upon pivotal movement of the carrier to its operative position,

`all of said gears being so positioned relative to one another that when the driving gear is engaged with the driven gear the line of action therebetween is substantially tangent to the driven gear, and power means for pivotally moving the carrier at a predetermined angular velocity such that when said carrier is pivoted to the operative position an initial angular velocity is imparted 10 to the rst carrier-mounted gear as it rolls about the driven gear, whereby the teeth of the second carriermounted gear are moving at substantially the same velocity and in the same direction as the teeth ofthe driving gear, these gears being thus synchronized and the teeth fully engaged before they are required to transmit power.

References Cited in the le of this patent UNITED STATES PATENTS 

